Printed indicia which are applied to T-shirts and other articles of clothing have become very popular in the last decade. Boutiques which specialize in printing fanciful indicia such as ornamentation, slogans, college names, or sports team names on T-shirts and other clothing are commonly seen in shopping malls. The indicia available at these boutiques can be pre-printed on a substrate and applied to articles of clothing purchased by the consumer with a heated press by boutique operators, or can be applied directly to an article of clothing. The indicia can comprise either simple one-color block letters or elaborate multi-color illustrations.
In common use in the industry in printing objects such as substrates or articles of clothing is a multi-station, turret type, printing press. The printing press of this type has a plurality of flat beds or platens spaced along its perimeter. Corresponding to each of these beds is a series of stations where a part of the indicia is alternately printed and cured on the object, i.e., substrate or article, being printed. The number of stations employed depends on the number of colors to be printed on the object. Indicia can consist of up to ten colors or more.
Also in common use are single station printing machines. Single station machines require the operator to print one color at a time using one screen at a time. After one color is printed on an object, the screen is removed and another screen placed thereon to print another color. As with the multi-station press, the new screen must be perfectly aligned with the preceding screen such that the image remains in registration. This single-stage process is very time-consuming, especially if multiple colors are used.
The most critical and time-consuming part of the screen printing process involving multiple colors is the alignment or registration of successive screens. Each screen for each color must be in registration with the other screens to ensure that the various colors do not overlap or are incorrectly spaced. Otherwise, the printed indicia will not be in registration, resulting in a skewed or imperfect indicia.